Respiratory monitoring is becoming an increasingly important tool in the monitoring, analysis, and treatment of the critical care patient. For example, anesthesiologists in the operating theatre, and attending physicians and nurses in intensive care and critical care units, depend more and more on respiratory monitoring as an essential indicator of the condition of the patient. Not surprisingly, increased frequency of use of respiratory monitoring techniques, tends to expand the method to more diverse populations of patients, and thus to place increasingly severe demands on the systems themselves, and upon those subsystems which avoid malfunction or system error. For example, there exists a wide disparity in respiratory quotient among patients of varying age (i.e., from neonate to octogenarian), physique, and relative robust health status. The respiratory monitoring systems themselves must be capable of responding to the widely varying parameters which are so involved, and so also must the subsystems avoid mistaking a malfunction or blockage artifact as a patient condition.
Conventional patient gas sampling systems include moisture detection devices designed to detect unwanted liquid transported from the patient. That is, conventional systems have the capacity to sense and measure vapor partial pressure of expired gases, and such readings would be severely compromised if free liquid, mucous, or the like materials were exposed to or lodged in the sensor. Thus, these systems have a need for, and generally include various sorts of devices which accumulate liquid at some point intermediate the patient and the analyzer, and which have the capacity for line purging once a predetermined amount of liquid has become entrapped. Generally, these devices need to be compact, low volume, disposable, and minimally intrusive to the flow of gases from the patient to the analyzer. Ideally, the structure and volume of the devices support laminar flow conditions, and avoid fluid mixing and consequent dilution of the gas "signal" to be measured and analyzed. Prior art examples of such devices include those set forth in U.S. Pat. Nos. 4,197,858 to Osborn, and 4,270,564 to Blackburn et al.
It is a primary object of the present invention to provide disposable, convenient moisture detection devices for respiratory monitoring systems, which are minimally intrusive to the laminar flow of gases, which have minimal liquid collection volumes, and are characterized by high sensitivity at very rapid response rates.